The present patent application is a continuation-in-part of copending commonly assigned application Ser. No. 469,973.
This invention relates to improved zinc alloys and is particularly directed to a method of providing a zincbase alloy stock material having improved tensile strength and ductility at ambient temperatures and to the zinc-base alloy stock material produced thereby.
Zinc generally has been regarded as a metal with properties that render it unsuited for use in various stock articles. For example, zinc normally has low tensile strength and poor resistance to fracture at ambient temperatures and many formed articles which may be subjected to stresses at ambient temperatures accordingly have not heretofore been made commercially with zinc or zinc alloys.
Zinc generally is rolled at temperatures below 390.degree. F., because its rollability is decreased at higher temperatures. When zinc is alloyed with various metals it has been found that there is generally a decrease in rollability with the result that higher rolling temperatures must be used. At any rate, temperatures in excess of 520.degree. F., are not desirable since temperatures above that cause loss of mechanical properties of the rolled zinc alloy.
Hare, U.S. Pat. No. 3,676,115 discloses an alloy comprising zinc within the range 70-82 weight percent, aluminum in the range of 18-30 weight percent, and magnesium within the range greater than 0.05 to 0.25 weight percent. The alloy may contain up to 2 percent of one or more of the elements copper, nickel and silver. The patentee discloses for his zinc alloy composition a tensile strength of about 52,000 psi.
Chollet et al., U.S. Pat. No. 3,741,819 relates to an alloy consisting of 18-30 percent aluminum, up to 3 percent copper, up to 0.10 percent magnesium, up to 0.10 percent lithium, and the balance zinc. The patentee discloses a method of heat treating this alloy to enhance properties thereof by slow cooling the alloy from between about 380.degree. C., and about 290.degree. C. The Chollet et al., patent discloses a tensile strength for thier alloy of 43,600 psi.
Winter et al., U.S. Pat. No. 2,169,441 disclose that the working of an alloy comprising Zn-Al-Cu-Mg at a temperature ranging from 518.degree. to 716.degree. F., improve the machinability, tensile and impact strength of said composition. However, the relatively high copper content of this alloy and the disclosed annealing temperatures do not permit the production of a product with high tensile strength that can be obtained by the method of the present invention.
Gervais et al., U.S. Pat. No. 3,793,091 disclose that ternary and quaternary zinc-aluminum alloys are conditioned to exhibit superplastic behavior by hot-working thereof at temperatures between about 400.degree. F., and the eutectoid temperatures of the alloy. The alloys of Gervais et al., are conditionable via rapid ice water quenching methods followed by hot working.